Moral, legal and practical considerations can present themselves in an instant. Faced with an ill fellow passenger, even doctors might pause.

Question: On a recent flight from Los Angeles to Shanghai, an older woman passenger collapsed on my lap and then on my feet. The flight crew had to bring an oxygen tank to her. It was terrifying, and I didn't know what to do. If this ever happens again, what should I do?

Kevin Orbach

Nantong, China

Answer: The quick answer is to summon help, stay calm and do what you can, which sounds simple but isn't. What you are required to do, what you can do and what you should do are different questions, so we'll start with the easiest one first.

The Federal Aviation Administration doesn't regulate a passenger's emergency response, said Ian Gregor, an FAA spokesman. But, he noted, "we have very specific requirements on the amount and type of medical supplies airlines have to keep on board, depending on the seating capacity of the plane, as well as crew member training."

Remember that flight attendants' first responsibility is safety and that first-aid training, including CPR training, is part of the package. Many aircraft of a certain size now carry defibrillators on which flight crews are trained. Some airlines also maintain air-to-ground contact with physicians who can help with instructions.

What you can do depends on your training. If you're a frequent traveler — heck, if you're a person who, say, gets up in the morning and goes outside — you should have basic first-aid training; if you haven't had a refresher course recently, book one. (Check community organizations for a class. The American Red Cross, among others, offers such training at a cost; go to http://www.lat.ms/RuMXP7 for info.)

After the shootings in Tucson in 2011, New York Times travel columnist Joe Sharkey noted that "lives literally were saved by the immediate response of a surprising number of ordinary citizens who happened to have been trained in basic first aid." He went on to advocate first-aid training centers in airports. What better way, he reasoned, to spend those dull hours than by learning a skill that could pay off? In an email to me, he said no airport had yet taken up the suggestion.

Perhaps you're thinking you should leave medical emergencies to the pros? In the best of all possible worlds, maybe yes. But Dr. Joel Schlessinger, a board-certified dermatologist in Omaha and chief executive of LovelySkin.com who also has emergency room training, said in an email that some physicians "don't have the knowledge to manage a complex and critical medical problem."

"There are many different skill sets in physicians," he said, "and some tend to shy away from acute care/management due to their personalities."

If a medical pro doesn't volunteer, "you do the best you can within the scope of your expertise," said Dr. Michael Zimring, a travel doctor at Mercy Medical Center in Baltimore.

What about legally? Can you be held responsible if something goes awry? "The majority of states have some form of a good Samaritan law," said Bob Bourgeois, an attorney who specializes in aviation litigation for Banker Lopez Gassler PA, based primarily in Tampa, Fla. (The laws, however, may differ in the amount of protection.)

Released from liability, should you help? "Morally," Zimring said, "it is the right thing to do."

Which makes Sharkey's idea the best idea to come along since airport charging stations.

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